System and method of tracking a mobile device

ABSTRACT

Systems and methods for tracking mobile devices are provided. One system comprises at least one processor and memory storing code which when executed by the at least one processor configure the at least one processor to perform a method of tracking a mobile device. The method comprises receiving broadcasting an IMSI message, receiving an IMSI attach request message from a mobile device, and identifying the mobile device within a location area.

This application is a continuation of U.S. patent application Ser. No.17/026,733 filed Sep. 21, 2020, which is a continuation of Ser. No.16/569,180 filed Sep. 12, 2019, which claims the benefit of U.S.Provisional Patent Application No. 62/730,287 filed Sep. 12, 2018, allof which are herein incorporated by reference in their entirety.

FIELD

The present disclosure generally relates to tracking devices, and inparticular to a system and method of tracking a mobile device.

INTRODUCTION

Unauthorized individuals may attempt to enter a premises. It isdesirable to be able to track individuals that attempt to enter apremises.

SUMMARY

In accordance with an aspect, there is provided a system for tracking amobile device. The system comprises a processor and memory storing codewhich when executed by the processor configure the processor tobroadcast an international mobile subscriber identity (IMSI) message;receive an IMSI attach request message from a mobile device, andidentify the mobile device within a location area.

In accordance with another aspect, there is provided a method fortracking a mobile device. The method comprises broadcasting an IMSImessage, receiving an IMSI attach request message from a mobile device,and identifying the mobile device within a location area.

In this respect, before explaining at least one embodiment in detail, itis to be understood that the embodiments are not limited in applicationto the details of construction and to the arrangements of the componentsset forth in the following description or illustrated in the drawings.Also, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of description and should not beregarded as limiting.

Many further features and combinations thereof concerning embodimentsdescribed herein will appear to those skilled in the art following areading of the instant disclosure.

DESCRIPTION OF THE FIGURES

Embodiments will be described, by way of example only, with reference tothe attached figures, wherein in the figures:

FIG. 1 illustrates, in a schematic diagram, an example of a trackingsystem architecture, in accordance with some embodiments;

FIG. 2 illustrates, in a flowchart, an example of a method of tracking amobile device, in accordance with some embodiments;

FIG. 3 illustrates, in plot diagrams, temporary mobile subscriberidentity (TMSI) distribution of mobile devices serial numbers (SNs) inEurope;

FIG. 4 illustrates, in a sequence diagram, an example of a method of theinterception of a message showing an international mobile subscriberidentity (IMSI) Attach capture, in accordance with some embodiments;

FIG. 5 illustrates, in a sequence diagram, an example of a method of alocation update capture, in accordance with some embodiments;

FIG. 6 illustrates, in a state transition diagram, an example of a stateinteraction for Global Systems for Mobile communication (GSM) packets ascaptured in a Finite State Machine (FSM), in accordance with someembodiments; and

FIG. 7 is a schematic diagram of a computing device such as a server.

It is understood that throughout the description and figures, likefeatures are identified by like reference numerals.

DETAILED DESCRIPTION

Embodiments of methods, systems, and apparatus are described throughreference to the drawings.

The Third Generation Partnership Project (3GPP) specification for Layers2 & 3 of the Global Systems for Mobile communication (GSM) protocol maybe loose in specific sections—causing network operators to haveimplementation deficiencies. These built-in differences and deficienciesallow for surface layer identification and passive tracking. Intrudersor trespassers may be passively tracked and identified on varyingproperties through the use of GSM signals emitted by their cellulardevices. In some embodiments, a software-defined radio (SDR) may bedeveloped to track such cellular devices. An SDR may comprise hardware,which is able to receive (listen) to the frequencies in the GSM band,coupled with in-house algorithms implemented in software to make senseof the data.

Before a capture can take place, a hardware device may be used tochannel in the GSM frequencies from the radio-link through an Uminterface. The hardware device may be configured to detect GSM andLong-Term Evolution (LTE) frequencies. In some embodiment, a hardwaresystem may be used to connect with the Um interface. In someembodiments, an SDR may be used to connect with the Um interface, wherethe tuning functionality is implemented in software. This SDR may becoupled with an Omni-directional antennae to feed into a monitoringsystem.

FIG. 1 illustrates, in a schematic diagram, an example of a devicetracking system 100 architecture, in accordance with some embodiments.The system 100 includes hardware (HW) 110 and software (SW) 120components. The hardware components 110 include an antenna 112 and aregister-transfer level (RTL)-SDR device 114. The software components120 include a GR-GSM 122 module, a scan tool 124, a user datagramprotocol (UDP) server 126, a database 128 and a UDP client 130.

FIG. 2 illustrates, in a flowchart, an example of a method 200 oftracking a mobile device, in accordance with some embodiments. Themethod comprises broadcasting 202 an IMSI message, receiving 204 an IMSIattach request message from a mobile device, and identifying 206 themobile device. Other steps may be added to the method 200.

In addition to the RTL-SDR 114 hardware, there is functionality tolisten to Bluetooth™ Low Energy (BLE) packets (e.g., in sniff mode),which has the dual functionality of identifying “friendlies” andintruders alike. The use case presented herein includes a BLE card thatcan be sensed on the premises to determine if employees have entered aparticular region. As will be detailed further below, this can also aidin distinguishing intruders from those who can legally enter, or havethe right be on, the premises.

The software 120 in the system 100 may route, dissect and performstateful inspection of GSM/LTE packets. The system 100 may be used todetermine who (generically) is on the property, and approximately (toproduce an n-sigma distance—statistically) where they are. Since the3GGP standard leaves implementation dependent behavior, this allows thesystem 100 leeway from the GSM perspective of stateful inspection. Aprinciple of cellular communication is the ability to identify a mobilestation (MS) on the serial number (SN). The international mobilesubscriber identity (IMSI) is a component that provides for uniqueidentification. Due to security concerns, the IMSI rarely broadcasts. Asa result the temporary mobile subscriber identity (TMSI)/Packet (P)-TMSIand the global unique temporary identifier (GUTI) (i.e., for LTE/FourthGeneration (4G)) is broadcast. It should be noted that thesereplacements for the IMSI are randomly generated and in some cases use auniform distribution. They are 32-bits long and can take on any valuefrom the set over which 32-bits (unsigned) are defined except for0xFFFFFFFF (used for subscriber identity module (SIM)). For a givenlocation area code (LAC) and MSs in the area, regeneration of the sameTMSI/P-TMSI/GUTI (herein referred to as TMSI) is not likely. Thisproblem then becomes random sampling on U for size X=2{circumflex over( )}32−1 and sample size Y (i.e., the Birthday Problem). For example:P(Z(i))=P(N(i)≤1)=(1−X ⁻¹)^(Y) +Y(1−X ⁻¹)^(Y-1)(1/X)where Z(i) is 1 when there is another TMSI duplicated from [0,U]exclusive of the special value 0xFFFFFFFF, and 0 otherwise. Then, theequation may be equally derived for the expected value for a collisionwith Y samples. Trivially, it is as follows:E(collisions)=Y+X(1−X ⁻¹)^(y) −Xwhich works such that Y MSs would have the possibility to have at most Ycollisions. Considering that ½³²−1 is near 10 billionths, the likelihoodfunction would work out that this is near impossible and highimprobable. Given 330 million people in the US all located in the sameLAC (if it was even theoretically possible) would still prove thelikelihood would be low (e.g., 7.69%). Thus, for sufficiently small Ythe likelihood drastically rolls off logarithmically.

This may then provide confidence to an algorithm that once a TMSI isobtained, it belongs to a particular MS for the given session in thespecific LAC in which the system 100 is listening. FIG. 3 illustrates,in plot diagrams, this TMSI distribution of mobile device serial SNs inEurope 300. As can be seen in the plot diagrams, the distribution isfairly even with the exception of a few points. Therefore, thelikelihood of a mobile device to have the same TMSI as another mobiledevice is very low.

Internally, the system 100 core may comprise stateful GSM packetinspection using a Finite Automaton. Times as to when IMSIs and TMSIsare broadcast through this inspection along with the 3GPP protocolspecification may be identified:

1. MS is in MS::IDLE state just entering an LA

2. MS is moving between two LAs

3. Paging Request (All types) in an LA

4. Location Update (Normal, Periodic, IMSI Attach)

5. Phone Switched Off (IMSI Detach)

6. CM Service Request (SMS, Broadcast)

The following outlines various software proposed solutions to handlethese cases and sub-cases for the GSM case.

For a Finite State Machine (FSM) this initially would be the firststate. MSs that come into the location area (LA) through various meanscould be marked: cellular switched on, SIM inserted, or network coveragerestored. This case is unique in that an MS will reach to the visitorlocation register (VLR). However, there are multiple cases, especiallyin remote areas, where the VLR is either down temporarily, low instatic-ram or not available, causing a hit to the home location register(HLR) and forcing the IMSI to be sent. Other cases such as a normalupdate where are pull from the VLR without HLR intervention still sendsthe IMSI (most likely the case is that VLRs internal cache was cleared)as seen, in the example of a GSM packet structure, below:

▾ GSM A-I/F DTAP—Location Updating Request

▾ Protocol Discriminator: Mobility Management messages (5)

-   -   . . . 0101=Protocol discriminator: Mobility Management messages        (0x5)    -   0000 . . . =Skip Indicator: No indication of selected PLMN(0)    -   00 . . . =Sequence number: 0    -   . . . 00 1000=DTAP Mobility Management Message Type: Location        Updating Request (0x08)

Ciphering Key Sequence Number

▾ Location Updating Type—Normal

-   -   . . . 0 . . . =Follow-On Request (FOR): No follow-on request        pending    -   . . . 0 . . . =Spare bit(s): 0    -   . . . 00=Updating Type: Normal (0)

Location Area Identification (LAI)

▾ Mobile Station Classmark 1

-   -   ▾ Mobile Station Classmark 1        -   0 . . . =Spare: 0        -   .10 . . . =Revision Level: Used by mobile stations            supporting R99 or later versions of the protocol (2)        -   . . . 1 . . . =ES IND: Controlled Early Classmark Sending            option is implemented in the MS        -   . . . 0 . . . =A5/1 algorithm supported: encryption            algorithm A5/1 available        -   . . . 011=RF Power Capability: class 4 (3)

▾ Mobile Identity—IMSI (310410530578733)

-   -   Length: 8    -   0011 . . . =Identity Digit 1:3    -   . . . 1 . . . =Odd/even indication: Odd number of identity        digits    -   . . . 001=Mobile Identity Type: IMSI (1)

▾ IMSI: 310410530578733

-   -   Mobile Country Code (MCC): United States (310)    -   Mobile Network Code (MNC): AT&T Mobility (410)

Now the ability to link an IMSI to a unique identifier in the system 100can be made. Furthermore, should the MS remain on a particular propertyin the LA once location updates happen (i.e., if the network operatorhas opted to follow specification) then multiple TMSIs (e.g., once every24 minutes) may be tied to an IMSI for the given session.

Two operations of system 100 implemented in software allow for thematching of an IMSI to a TMSI upon receipt of an IMSI Attach message bythe system 100 and passively tracking an MS through a complex set ofsub-states via a Location Update GSM Procedure. An internal Finite StateMachine will start off in the IMSI Attach state of which the system 100will then wait for messages that match the state and use the databasefor insert, deletion and retrieval of MS related (meta)data based onpacket analysis.

FIG. 4 illustrates, in a sequence diagram, an example of a method 400 ofthe interception of a message showing an IMSI Attach capture, inaccordance with some embodiments. The method 400 comprises a MS 10sending a RR3 Channel Request message 402 to a base station (BSS) 20.The BSS 20 sends a RR3 Immediate Assign (AGCH) message 404 to the MS 10.Next, the MS 10 sends an Identity (SDCCH) message 406 to the BSS 20. TheBSS 20 sends an Auth (SDCCH) message 408 to the MS 10. Next, the MS 10sends a RR3 IMSI Attach <TMSI> message 410 to a mobile station centre(MSC) 30. The MSC 30 then sends a MAP/B Attach IMSI <TMSI> message 412to a visitor location register (VLR) 40. The IMSI may be marked asactive. The VLR 40 sends an IMAP/B IMSI Attach Ack message 414 to theMSC 30. The MSC 30 then sends an IMSI Attach Ack message 416 to the BSS20. The BSS 20 sends a Disassemble IMSI Attach <IMSI/LAI> message 418 tothe system 100. The system 100 enters 420 a finite state machine (FSM)where the system 100 monitors the state of the IMSI and stores it in thedatabase 128. The system 100 then waits 422 for a matching TMSI.

System 100, for a majority of the time, will execute in the LocationUpdating State and the three sub-states: normal, IMSI Attach andperiodic (with Timer T3212). Moreover, a majority of the passivetracking and geolocation position awareness will happen through thesesub-states. Initially a message will trigger this state (particularly ifthe MS is already registered in the system 100 database).

FIG. 5 illustrates, in a sequence diagram, an example of a method 500 ofa location update capture, in accordance with some embodiments. Themethod 500 comprises the MS 10 sending a Channel Request <RACH> message502 to the BSS 20. The BSS 20 sends a DCCH Assign message 504 to the MS10. The MS 10 then sends a Location Update Request (SDCCH) message 506to the BSS 20. The BSS 20 sends a Location Update message 508 to the MSC30. The MSC 30 sends a Send <IMSI/TMSI+LAI> message 510 to the VLR 40.The VLR 40 sends a TMSI <Auth+Encryption A5/1> message to the MSC 30.The MSC 30 then sends 514 the TMSI to the BSS 20. The BSS 20 sends aDecode and Capture <TMSI+LAI> message to the system 100. The system 100enters 518 FSM and checks 520 for a TMSI match. The system 100 performsthe capture of TMSI and LAI information lookup using an on-site database(DB) 128 for +/−2 km geolocation information. Upon TMSI match checking,the application of a Hidden Markov Model (HMM) and Bayesian Filter (BF)may be used to improve distance and location trajectory calculations,consequently narrowing a 2 km distance to a value around approximately500 m (centered at the antenna) at most dependent on terrain andantennae properties.

FIG. 6 illustrates, in a state transition diagram, an example of a stateinteraction 600 for GSM packets as captured in a FSM, in accordance withsome embodiments. The states shown include an initial state 602, apaging requests types state 604, a location update reject state 606, aCM service state 608, an IMSI detach state 610, an immediate assignstate 612 and a location update state 620. The location update stateincludes a periodic sub-state 622, a normal sub-state 624 and a IMSIattach sub-state 626. The initial state 602 reflects a MS on a propertyas seen in an IMSI Attach message. The device (MS) may transition to anyof the states. During a state transition to a location update state, theHMM and BF system may determine a location of the device. The stateinteraction 600 may then be inputted into a machine learning (ML)algorithm for position determination.

In some embodiments, the system 100, can also listen to BL devices. Incases where users are given name Identification Cards with a picture ofthemselves on the card, a Bluetooth™ device may be attached to the IDcard which can be picked up by the system 100 platform. The identity ofthe person may be confirmed if the person's picture on the ID card isthe same by showing a picture of the person on the computer. Also, sincethere are instances in agriculture where individuals are allowed toenter properties after a given period (quarantine period), the system100 can be used to enforce these rules.

The system 100 can be used as a method of disease traceability forindividuals who often visit farm premises and maybe vectors of diseasespread. Since the system 100 can be used by many farmers, it is possiblethat if a farmer is part of an association, then that association groupcan create a network of movements. This would make it possible toidentify phone characteristics and track a mobile phone as it movesaround farm properties.

This type of movement tracking can also be applied outside ofagriculture and applied to other sectors such as in mining facilities,personal cottages, and other sectors which require an intrusiondetection system where assets are expensive.

FIG. 7 is a schematic diagram of a computing device 700 such as aserver. As depicted, the computing device includes at least oneprocessor 702, memory 704, at least one I/O interface 706, and at leastone network interface 708.

Processor 702 may be an Intel or AMD x86 or x64, PowerPC, ARM processor,or the like. Memory 704 may include a suitable combination of computermemory that is located either internally or externally such as, forexample, random-access memory (RAM), read-only memory (ROM), compactdisc read-only memory (CDROM).

Each I/O interface 706 enables computing device 700 to interconnect withone or more input devices, such as a keyboard, mouse, camera, touchscreen and a microphone, or with one or more output devices such as adisplay screen and a speaker.

Each network interface 708 enables computing device 700 to communicatewith other components, to exchange data with other components, to accessand connect to network resources, to serve applications, and performother computing applications by connecting to a network (or multiplenetworks) capable of carrying data including the Internet, Ethernet,plain old telephone service (POTS) line, public switch telephone network(PSTN), integrated services digital network (ISDN), digital subscriberline (DSL), coaxial cable, fiber optics, satellite, mobile, wireless(e.g. Wi-Fi, WiMAX), SS7 signaling network, fixed line, local areanetwork, wide area network, and others.

The foregoing discussion provides many example embodiments of theinventive subject matter. Although each embodiment represents a singlecombination of inventive elements, the inventive subject matter isconsidered to include all possible combinations of the disclosedelements. Thus, if one embodiment comprises elements A, B, and C, and asecond embodiment comprises elements B and D, then the inventive subjectmatter is also considered to include other remaining combinations of A,B, C, or D, even if not explicitly disclosed.

The embodiments of the devices, systems and methods described herein maybe implemented in a combination of both hardware and software. Theseembodiments may be implemented on programmable computers, each computerincluding at least one processor, a data storage system (includingvolatile memory or non-volatile memory or other data storage elements ora combination thereof), and at least one communication interface.

Program code is applied to input data to perform the functions describedherein and to generate output information. The output information isapplied to one or more output devices. In some embodiments, thecommunication interface may be a network communication interface. Inembodiments in which elements may be combined, the communicationinterface may be a software communication interface, such as those forinter-process communication. In still other embodiments, there may be acombination of communication interfaces implemented as hardware,software, and combination thereof.

Throughout the foregoing discussion, references are made regardingservers, services, interfaces, portals, platforms, or other systemsformed from computing devices. It should be appreciated that the use ofsuch terms is deemed to represent one or more computing devices havingat least one processor configured to execute software instructionsstored on a computer readable tangible, non-transitory medium. Forexample, a server can include one or more computers operating as a webserver, database server, or other type of computer server in a manner tofulfill described roles, responsibilities, or functions.

The technical solution of embodiments may be in the form of a softwareproduct. The software product may be stored in a non-volatile ornon-transitory storage medium, which can be a compact disk read-onlymemory (CD-ROM), a USB flash disk, or a removable hard disk. Thesoftware product includes a number of instructions that enable acomputer device (personal computer, server, or network device) toexecute the methods provided by the embodiments.

The embodiments described herein are implemented by physical computerhardware, including computing devices, servers, receivers, transmitters,processors, memory, displays, and networks. The embodiments describedherein provide useful physical machines and particularly configuredcomputer hardware arrangements.

Although the embodiments have been described in detail, it should beunderstood that various changes, substitutions and alterations can bemade herein.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification.

As can be understood, the examples described above and illustrated areintended to be exemplary only.

The invention claimed is:
 1. A system for tracking mobile devices, thesystem comprising at least one processor and memory storing code whichwhen executed by the at least one processor configure the at least oneprocessor to: receive a temporary mobile subscriber identity (TMSI) andlocation area identification (LAI) associated with an unidentifiedmobile device, the TMSI and LAI being part of a decode and capturemessage received from a base station; and identify the unidentifiedmobile device as being a mobile device within the location areaassociated with an active international mobile subscriber identity(IMSI).
 2. The system as claimed in claim 1, wherein to identify theunidentified mobile device, the at least one processor is configured to:enter a finite state mode; obtain a location update state of the IMSI,the location update state comprising one of: a location update normalstate; a location update IMSI attach state; and a location updateperiodic state; and identify a location update state associated with theTMSI as matching a location update state associated with the IMSI. 3.The system as claimed in claim 2, wherein the at least one processor isconfigured to: determine that the mobile device associated with the IMSIis still within the location area.
 4. The system as claimed in claim 1,wherein the at least one processor is configured to: apply a hiddenmarkov model and bayesian filter to narrow the location area.
 5. Thesystem as claimed in claim 1, wherein the at least one processor isconfigured to: monitor the location of the identified mobile device byobtaining periodic decode and capture messages for non-identified mobiledevices, said periodic decode and capture messages received at the basestation.
 6. The system as claimed in claim 1, wherein the at least oneprocessor is configured to: store IMSI location update stateinformation; and probabilistically compare TMSI location update stateinformation with the stored IMSI location update state information.
 7. Amethod of tracking mobile devices, the method comprising: receiving atemporary mobile subscriber identity (TMSI) and location areaidentification (LAI) associated with an unidentified mobile device, theTMSI and LAI being part of a decode and capture message received from abase station; and identifying the unidentified mobile device as being amobile device within the location area associated with an activeinternational mobile subscriber identity (IMSI).
 8. The method asclaimed in claim 7, comprising: entering a finite state mode; monitoringa location update state of the IMSI, the location update statecomprising one of: a location update normal state; a location updateIMSI attach state; and a location update periodic state; and identifyinga location update state associated with the TMSI as matching a locationupdate state associated with the IMSI.
 9. The method as claimed in claim8, comprising determining that the mobile device associated with theIMSI is still within the location area.
 10. The method as claimed inclaim 7, comprising: applying a hidden markov model and bayesian filterto narrow the location area.
 11. The method as claimed in claim 7,comprising: periodically monitoring the location of the identifiedmobile device by obtaining periodic decode and capture messages fornon-identified mobile devices, said periodic decode and capture messagesreceived at the base station.
 12. The method as claimed in claim 7,comprising: storing IMSI location update state information; andprobabilistically comparing TMSI location update state information withthe stored IMSI location update state information.
 13. A system fortracking mobile devices, the system comprising at least one processorand memory storing code which when executed by the at least oneprocessor configure the at least one processor to: receive a temporarymobile subscriber identity (TMSI) and location area identification (LAI)associated with an unidentified mobile device, the TMSI and LAI beingpart of a decode and capture message received from a base station; entera finite state mode; monitor a location update state of an activeinternational mobile subscriber identity (TASI), the location updatestate comprising one of: a location update normal state; a locationupdate IMSI attach state; and a location update periodic state; andidentifying a location update state associated with the TMSI as matchinga location update state associated with the IMSI.
 14. The system asclaimed in claim 13, wherein the at least one processor is configuredto: determine that the mobile device associated with the IMSI is stillwithin the location area.
 15. The system as claimed in claim 14, whereinthe at least one processor is configured to: apply a hidden markov modeland bayesian filter to narrow the location area.
 16. The system asclaimed in claim 15, wherein the at least one processor is configuredto: store IMSI location update state information; probabilisticallycompare TMSI location update state information with the stored IMSIlocation update state information; and periodically monitor the locationof the identified mobile device by obtaining periodic decode and capturemessages for non-identified mobile devices, said periodic decode andcapture messages received at the base station.
 17. A method for trackingmobile devices, the method comprising: receiving a temporary mobilesubscriber identity (TMSI) and location area identification (LAI)associated with an unidentified mobile device, the TMSI and LAI beingpart of a decode and capture message received from a base station;entering a finite state mode; monitoring a location update state of anactive international mobile subscriber identity (IMSI), the locationupdate state comprising one of: a location update normal state; alocation update IMSI attach state; and a location update periodic state;and identifying a location update state associated with the TMSI asmatching a location update state associated with the IMSI.
 18. Themethod as claimed in claim 17, comprising: determining that the mobiledevice associated with the IMSI is still within the location area. 19.The method as claimed in claim 18, comprising: applying a hidden markovmodel and bayesian filter to narrow the location area.
 20. The method asclaimed in claim 19, comprising: storing IMSI location update stateinformation; probabilistically comparing TMSI location update stateinformation with the stored IMSI location update state information; andperiodically monitoring the location of the identified mobile device byobtaining periodic decode and capture messages for non-identified mobiledevices, said periodic decode and capture messages received at the basestation.